Hey I'm stuck on this!

(7) A ball of paper falls from the top of the CN Tower. Its height, h, above the ground in meters after t seconds is given by h(t) = 603 - Vt2 + 9, t 2 0. (a) Determine the height of the ball of paper after 4 seconds. (b) Find the average rate of change of the ball of paper from t= 10 seconds to t = 20 seconds. (c) Find the instantaneous rate of change at 4 seconds. (d) How fast is the ball falling when its height is 100 meters